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On the Calculation of Stresses in the Hulls of Rigid Airships

Published online by Cambridge University Press:  24 August 2017

R. V. Southwell
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Extract

An essay which is to be submitted in competition for the R.38 Memorial Prize may fairly presume a knowledge of airship history in recent years, and I shall here touch only on those circumstances which have influenced the writing of this paper. Between the cessation of airship construction in the autumn of 1921 and its revival in the summer of 1924, all branches of official research were discontinued by order of the Air Council, excepting an inquiry into the theoretical aspects of stress-calculation which had been urged by the Aeronautical Research Committee in its report on the disaster to R.38.

Type
Research Article
Information
The Aeronautical Journal , Volume 30 , Issue 191 , November 1926 , pp. 627 - 667
Copyright
Copyright © Royal Aeronautical Society 1926

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References

Note on page 629 * By “ effect ” may be understood either stress, strain or displacement.

Note on page 631 * The “ Method of Least Work ” is thus shown to be, in essentials, identical with the “ Method of Comparison of Deflections ” which is frequently used as an alternative. Cf. W. S. Farren, Aeronautical Research Committee R. & M. No. 769.

Note on page 631 † Phil. Mag., January, 1923.

Note on page 632 * We may assume that the equilibrium of the structure is stable under any applied system of external loads.

Note on page 632 † In the paper cited, a corresponding proof was advanced to justify the method proposed by Castigliano for use in the more general case, where the conditions are such that the initial strains have specified values.

Note on page 633 * R. & M. 800, § 4.

Note on page 633 † Cf. the Report of the Airworthiness of Airships Panel, R. & M. 970.

Note on page 633 ‡ That is, the triangle formed by joining three nodes by straight lines.

Note on page 634 * This section is based on a more detailed discussion which is given in my paper on “ Primary Stress-Determination in Space Frames ” (Engineering, February 6th, 1920).

Note on page 636 * Loc. cit., § 2.45, footnote.

Note on page 636 † R. & M. 737, § 4; R. & M. 821, § 9.

Note on page 636 ‡ For a member of uniform cross-section A, Young's Modulus E, Ω = EA/l3.

Note on page 637 * Also published as R. & M. 821 of the Aeronautical Research Committee.

Note on page 637 † It is a fallacy sometimes encountered in conversation, that the buoyancy of an airship is derived from the upward pressure of the hydrogen. That this is not strictly correct will be apparent when it is recognised that a greater lifting power would be obtained if the hydrogen could be replaced by a vacuum.

Note on page 638 * I am indebted to the Design Staff of the Royal Airship Works, Cardington, for kindly supplying this diagram.

Note on page 640 * In the actual framework, where these members are subjected to lateral (i.e., “ secondary”) loading throughout their length, some degree of curvature may be desirable; at the bow, where the external surface of the hull must have considerable curvature, special devices are introduced to render the longitudinals effectively straight in the structural sense—i.e., to arrange that they shall behave under, compression as straight, and not as bowed struts.

Note on page 642 * Trans. Roy. Irish Acad., Vol. XXII (1854), pp. 343-377. A summary of this paper is given in Appendix II. of Dr. R. Jones’ report “ On the Aerodynamic Characteristics of Parachutes, etc.” (R. & M. 862).

Note on page 643 * Indeed, we may go further, and assert that the member may with close approximation be replaced by a constraint. Cf. Rayleigh, Scientific Papers, Vol. IV, p. 451.

Note on page 643 † R. & M. 800.

Note on page 644 * R. & M. 819. p. 3.

Note on page 645 * R. & M. 737, 790, 791 and 819.

Note on page 645 † Cf. A. E. H. Love, Mathematical Theory of Elasticity, Chapters XIV, XV.

Note on page 645 ‡ Cf. R. & M. 800, § 12.

Note on page 645 § Cf. my paper “ On Castigliano's Theorem of Least Work, and the Principle of St. Venant,” loc. cit., § 8.

Note on page 645 ‖ R. & M. 800, § 12.

Note on page 646 * R. & M. 819, p. 4.

Note on page 646 † Appendix VII contained a detailed account, illustrated by examples, of the “ Method of Least Work ” (§ 2.3).

Note on page 646 ‡ Cf. R. & M. 800, p. 52.

Note on page 646 § § Ibid., p. 7.

Note on page 646 ‖ Ibid., p. 52.

Note on page 647 * T. 1946 (unpublished).

Note on page 648 * T. 1946a (unpublished).

Note on page 648 † Because the effect is in actual fact shared between this panel and the remainder of the hull structure.

Note on page 648 ‡ Appendix to T. 2036 (unpublished).

Note on page 649 * R. & M. 971 (May, 1925). Cf. also Prof. Pippard's paper read to the R.Ae.Soc. on January 7th, 1926.

Note on page 649 † Loc. cit.

Note on page 652 * T. 1967 (unpublished).

Note on page 653 * “ The Calculation of Stresses in a Redundant Structure by the Method of Comparison of Deflections, etc.,” October, 1921.

Note on page 656 * * The term employed by Saint Venant in the enunciation of his well-known “ principle.” Cf. A. E. H. Love, op. cit., §8q.

Note on page 659 * ” The Stresses in a Circular Ring.” Selected Engineering Paper No. 12 (1924) of the Institution of Civil Engineers.

Note on page 659 † Ibid., p. 4.

Note on page 661 * Cf. R. & M. 80Q, Appendix VIL

Note on page 661 † R. & M. 800.

Note on page 664 * Trans. Roy. Irish Acad., Vol. XXII (1854), pp. 343–377. Some notes on this paper were given in a paper (T. 1345) “ On the Shapes of Parachutes and Other Non-Rigid Envelopes,” communicated in 1919. Cf. footnote, § 3.2.

Note on page 666 * If two wires cross, and neither wire changes its direction at the junction, it is easily seen that neither tension has its value altered there.